Hydraulic forming methods are generally used as manufacturing methods, notably for pieces of complex forms. They involve using the pressure of a fluid, preferably a liquid, to produce the plastic deformation of a steel plate held in a mold. The fluid then acts on the steel plate to make it follow the form of the mold. This fluid can be pressurized in various ways.
Among the existing hydraulic forming methods, the electrohydraulic forming method, called EHF method, can be cited. This method is a very high speed deformation forming method which is based on an electrical discharge of a high energy stored in capacitors either between two electrodes placed in a chamber filled with fluid, or in an explosive wire placed in a chamber filled with fluid. When an electrical discharge is created in the fluid, a shockwave is generated in said fluid, it is propagated and projects the steel plate against the mold. The dynamic pressure thus generated on the steel plate allows the high speed deformation of its constituent material which is projected against the mold, thus allowing the forming thereof.
Such a method makes it possible to form steel plates but also other pieces produced in a plastically deformable material. It is used to produce pieces of large dimensions, that is to say pieces whose characteristic length is significantly greater than a distance between the two electrodes.
Such a method offers numerous advantages, notably the obtention of very fine details on the pieces, such as, for example, etchings, the absence of elastic return, or even low manufacturing costs.
However, one of the drawbacks lies in the cycle time necessary for the forming of a piece, as indicated in the U.S. Pat. No. 7,493,787. In effect, as is known, a forming cycle via the EHF method breaks down into several steps:                placement of the piece to be formed in an electrohydraulic forming chamber,        filling a hollow chamber in the electrohydraulic forming chamber with a fluid,        electrohydraulic discharge into the fluid contained in the hollow chamber,        draining of the hollow chamber,        removal of the formed part.        
The steps of filling and draining of the hollow chamber represent the most time-consuming steps.